Method for the pictorial coloring of wood surfaces and a colored wood substrate

ABSTRACT

In order to provide, in a contemporary manner, inlays in which the character of the wood is retained, a process method applies a stain containing acrylates or polyacrylates to a wood substrate in a first step. After a drying time, in a further step, a mordant dye that reactively binds with the wood substrate and with the stain that has penetrated into the wood substrate is applied to the wood substrate.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuing application, under 35 U.S.C. §120, of copending international application No. PCT/EP2004/005269, filed May 17, 2004, which designated the United States; this application also claims the priority, under 35 U.S.C. §119, of German patent application No. 103 22 767.9, filed May 19, 2003; the prior applications are herewith incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

The invention relates to a method for the pictorial coloring of wood surfaces. Such a method is also referred to below as a method for the production of technical inlays.

A method for coloring wood is disclosed, for example, in published, non-prosecuted German patent application DE 36 18 463 A1. Here, the work piece to be colored is impregnated with a mordant dye. The production of pictorial, structured surfaces that give the impression of inlays is not intended according to this method.

Inlays are usually understood as meaning inlay work of different-colored wood or another type of material, such as, for example, tortoise shell, mother of pearl, metal or glass, in depressions which are made in solid wood. Another inlay technique is the laying of a decorative veneer on a wood core, the decorative veneer being composed of material of different colors or different types. In the 18th century, these inlay techniques were replaced by so-called inlay painting. The basis of this is the fixing of ornaments applied with watercolors by a glue or polish coat.

Published, non-prosecuted German patent application DE 26 03 114 describes a method for the production of inlay-like prints on wood. The essential feature of this method is that it is a printing method. In other words, the impression of an inlay is produced by applying printing ink to the surface of the wood to be printed. In terms of the overall impression, such inlay-like prints cannot be compared with actual inlay work, and it is for this reason that the method also has not become established on the market.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a method for the pictorial coloring of wood surfaces and a colored wood substrate which overcome the above-mentioned disadvantages of the prior art methods and devices of this general type, which provides, in a contemporary manner, high-quality technical inlays, i.e. wood surfaces which are colored in a pictorial manner and can be produced rapidly and economically.

With the foregoing and other objects in view there is provided, in accordance with the invention, a method for coloring a wood substrate. The method includes the steps of providing the wood substrate, applying a stain containing acrylates or polyacrylates to the wood substrate, and producing a motif structure by applying a mordant dye to the wood structure which reactively binds with the wood substrate and with the stain which previously has penetrated into the wood substrate.

The object is achieved by providing a method in which a stain is applied to a wood substrate in a first step. Here, the wood substrate may be solid wood or a laminated or unlaminated wood-base material. Wood-base material is understood as meaning, for example, a particleboard, a wood fiber board or plywood, in particular a veneer board or block board. The stain contains acrylates and/or polyacrylates and can be spread, brushed, applied with a doctor blade, rolled, sprayed or otherwise applied, for example by immersion, onto the wood substrate. In the subsequent drying time, the stain spreads in the wood substrate and binds to the wood surface. The stain used is a liquid or suspension which, in its chemical composition, permits a reaction with the wood substrate and with the dye subsequently applied in a further step to the wood substrate and hence coloring of the wood. The result is referred to as technical inlay.

The dyes used are so-called mordant dyes which, completely surprisingly, turn out to be particularly suitable for the production of technical inlays. Mordant dyes are understood as meaning a group of dyes that have been widely used since the Middle Ages but is more rarely used today owing to the required technical complexity. Mordant dyes belong to various classes of substances and have been used to date virtually exclusively in the textile industry, predominantly for dyeing wool, silk, cellulose fibers and other protein fibers. Not to be confused with the mordant dyes used here, are the so-called dye stains, which have long been known as colorants for wood.

Advantageous further developments of the invention use selected stains to make the method according to the invention particularly environmentally friendly. The stain used is preferably oil-free and, with the exception of water, has no inorganic components at all, such as, for example, chromium, nickel or silicon. The use of toxic solvents is therefore not required. The solids content of the stain is preferably in a range between 30% and 70%. A solids content of about 60 to 65% has proven to be particularly advantageous. However, depending on the application, results of sufficient quality are also obtained in the case of a low solids content of about 30%. By using a water-based stain, the method according to the invention can also be used in critical fields of use, for example in the food sector. The water-soluble stain is free of toxins and is biodegradable, so that in particular the disposal of residues is also possible without problems. Particularly good results are obtained with stains that contain acrylates or polyacrylates as substantial components. In a preferred embodiment of the invention, the finished stain is obtained from a stain concentrate that is diluted with water. The stain concentrate preferably is formed of from 60 to 90% by weight of ethyl acrylate and from 10 to 40% by weight of butyl acrylate mixed with water, at a solids content of about 63%. This concentrate is then diluted with water in the ratio of from 1:3 to 1:5 before use. In the mixture of acrylates and water, polymerization reactions can take place so that the water content or solids content of the mixture obtained by dilution is not necessarily obtained arithmetically from the composition of the starting materials.

Preferably used mordant dyes are anthraquinone dyes, in particular alizarin dyes. An advantage of these dyes is that they are free of halogens and amines and are therefore neither carcinogenic nor hazardous to health. All substances used in the method according to the invention are therefore safe from environmental and health points of view.

Application of the mordant dye by vapor deposition is particularly advantageous, the mordant dye being converted into the gaseous state by sublimation. Particularly advantageous in this context is the use of an intermediate carrier, in particular in the form of a sublimation element, in particular a coated sublimation element, provided with the mordant dye. The application of the mordant dye to the wood substrate is effected in these cases preferably with the aid of a press, for example a veneer press, as used, for example, by carpenters. Under the influence of the required pressure and temperature values, sublimation of the mordant dyes takes place. The mordant dyes are released from the sublimation element, which was placed beforehand on the wood substrate to be colored, and are applied to the wood substrate. The sublimation element serves as a carrier material for the mordant dyes. At the same time, the water evaporates from the previously applied stain. The stain, mordant dye and wood substrate bind reactively in such a way that, after the end of the pressing process, the dye is present in a fixed and irrecoverable form in the wood. After the application of the mordant dye, a thin protective layer or a lacquer, for example PU can be applied to the wood substrate in order to protect the surface from environmental influences and wear.

The present method permits particularly environmentally friendly and hence contemporary coloring of wood. At the same time, the method is completely safe with regard to health. In contrast to all methods known to date, there is no covering or sealing of the wood surface by a color print. Rather, coloring is affected by penetration of the substance used into the wood, with the result that high-quality technical inlays can be produced. A particular feature of the coloring result is that the surface character and the haptic properties of the wood are fully retained. Color fastness and light fastness of the technical inlays thus produced correspond to those of printing processes.

By the present method, it is not only possible to provide wood substrates with uniform coloring over the entire area. The application of pictorial motifs having very fine motif structures of the order of magnitude of a few millimeters is also possible without the colors running into one another. The method is particularly simple to carry out and therefore economical. It can be carried out using existing work machines and apparatuses, with the result that introduction of the method or conversion of existing methods to the method according to the invention is possible without major capital costs. The visually very appealing results are very close to those of conventional inlays but are much more economical in their production since mass production is possible without problems.

Wood substrates having technical inlays can be economically produced and widely used. Such wood substrates can be used, for example, in the production of decorative or utility furniture and in the building trade or in other fields of use where a colored wood surface is desired.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in a method for the pictorial coloring of wood surfaces and colored wood structures, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram of a method for staining a wood substrate according to the invention; and

FIG. 2 is a diagrammatic, perspective view of a wood substrate colored by the method according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In all the figures of the drawing, sub-features and integral parts that correspond to one another bear the same reference symbol in each case. Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is shown a greatly simplified flow diagram of the method according to the invention. In a first step 10, an oil-free, water-soluble stain is applied to a wood substrate in the form of a veneer board by spraying. The stain is free of inorganic components and is obtained from a stain concentrate which is diluted in the ratio of 1:4 with water and, at a solids content of 63%, is formed of 70% by weight of ethyl acrylate and 30% by weight of butyl acrylate. After the application of the stain to the wood substrate, drying of the stain that has penetrated into the substrate surface is effected in a subsequent step 11. The drying is preferably effected at room temperature so that no energy costs are incurred for drying. The drying process can alternatively also take place at elevated temperatures, for example in the range from 100° C. to 150° C. Depending on the drying temperature, the drying time is between a few minutes and a few hours.

After the drying, an alizarin dye is applied to the wood substrate. The application is effected in step 12 using a conventional veneer press. Typical press parameters are, for example, a press pressure of from 5 to 15 bar and a temperature of, for example, 180° C., which can be achieved by electric heating of the press. Instead of a veneer press, it is of course also possible to use other suitable presses or apparatuses which permit evaporation of the mordant dyes and densification of the dyes in the wood substrate and a reactive bond between the stain, the mordant dyes and the wood.

Instead of the evaporation of the mordant dyes onto the wood substrate by an intermediate carrier, direct vapor deposition onto the wood substrate can of course also be effected. In a final step 13, a PU protective layer is finally applied to the colored surface of the wood substrate, the surface being protected from environmental influences.

Finally, FIG. 2 shows a greatly simplified illustration of a wood substrate 1 in the form of a veneer board that is provided with technical inlays that are produced by the method according to the invention.

The wood substrate substantially contains a veneer carrier 2, on the top of which a veneer 3, for example a maple veneer, is mounted in a conventional manner. The stains and mordant dyes applied to the wood substrate 1 in steps 10 and 12, respectively, have penetrated into the veneer 3 and formed a bond with the wood. A sharp separation line 4 separates veneer regions 5, 6 of different colors. Finally, a PU protective layer 7 that seals the wood substrate 1 on the outside is applied to the veneer 3. 

1. A method for coloring a wood substrate, which comprises the steps of: providing the wood substrate; applying a stain containing a material seletected from the group consisting of acrylates and polyacrylates to the wood substrate; and producing a motif structure by applying a mordant dye to the wood structure which reactively binds with the wood substrate and with the stain which previously has penetrated into the wood substrate.
 2. The method according to claim 1, which further comprises producing the stain from a mixture containing ethyl acrylate and butyl acrylate.
 3. The method according to claim 1, which further comprises forming the stain to be oil-free.
 4. The method according to claim 1, which further comprises forming the stain to be free of inorganic components.
 5. The method according to claim 1, which further comprises obtaining the stain from a stain concentrate having a solids content of less than 70%.
 6. The method according to claim 1, which further comprises obtaining the stain from a stain concentrate having a solids content of at least 30%.
 7. The method according to claim 1, which further comprises forming the stain to be water-soluble.
 8. The method according to claim 1, which further comprises using an anthraquinone dye as the mordant dye.
 9. The method according to claim 8, which further comprises using an alizarin dye as the mordant dye.
 10. The method according to claim 1, which further comprises performing a vapor deposition process for applying the mordant dye onto the wood substrate.
 11. The method according to claim 10, which further comprises using an intermediate carrier during the performing step.
 12. The method according to claim 11, which further comprises providing a sublimation element as the intermediate carrier with the mordant dye intended for conversion into a gaseous state.
 13. The method according to claim 11, which further comprises using a heatable press.
 14. A colored wood substrate, comprising a wood substrate; a stain containing a material seletected from the group consisting of acrylates and polyacrylates applied to said wood substrate; and a mordant dye applied to said wood structure for reactively binding with said wood substrate and with said stain which has penetrated into said wood substrate resulting in a motif structure having a nonuniform coloring. 